military struggle fought on the Korean Peninsula from June 1950 to July 1953. Begun as a war between South Korea (Republic of Korea) and North Korea (Democratic People’s Republic of Korea), after the North’s invasion of the South, the conflict swiftly developed into a limited international war involving the U.S. and 19 other nations. From a general viewpoint, the Korean War was one of the by-products of the cold war, the global political and diplomatic struggle between the Communist and non-Communist systems following World War II. The motives behind North Korea’s decision to attack South Korea, however, had as much to do with internal Korean politics north and south of the 38th parallel (the boundary between the two republics) as with the cold war. Contrary to the prevailing view at the time, North Korea apparently attacked South Korea without the knowledge of either the Soviet Union or the People’s Republic of China. The Soviet Union, which expected a war at a later time, was boycotting the United Nations (UN) when the attack occurred. The Communist government of China, meanwhile, was hoping to invade the island of Taiwan without having to deal with a military response from the U.S.

Considerable civil strife south of the 38th parallel and growing opposition to South Korea’s president, Syngman Rhee, persuaded the North Korean leader, Kim Il Sung, that he would be welcomed by many South Koreans as a liberator intent on overthrowing the Rhee government and reuniting the two Koreas. As a champion of Korean unification, Kim would also undermine ongoing opposition to his own regime in North Korea.

The war began on June 25 when the North Korean army, substantially equipped by the Soviet Union, crossed the 38th parallel and invaded South Korea. The U.S. immediately responded by sending supplies to Korea, and it quickly broadened its commitment in the conflict. On June 27 the UN Security Council, with the Soviet Union voluntarily absent, passed a U.S.-sponsored resolution calling for military sanctions against North Korea. Three days later, U.S. President Harry S. Truman ordered combat forces stationed in Japan deployed to Korea. American forces, those of South Korea, and, ultimately, combat contingents from Australia, Belgium, Luxembourg, Canada, Colombia, Ethiopia, France, Great Britain, Greece, the Netherlands, New Zealand, the Philippines, South Africa, Thailand, and Turkey, with medical units from Denmark, India, and Sweden, were placed under a unified UN command headed by the U.S. commander in chief in the Far East, Gen. Douglas MacArthur. The participating ground forces of these nations, the U.S., and South Korea were grouped in the U.S. Eighth Army. The action was unique because neither the UN nor its predecessor, the League of Nations, had ever used military measures to repel an aggressor.

Even after Truman committed American ground forces to Korea, the war continued to go badly. Before the North Koreans were stopped in August, they had captured Seoul, the capital of South Korea, and the Americans and South Koreans had been pushed back to a small perimeter around the southern port city of Pusan, extending about 129 km (about 80 mi) from north to south and about 80 km (about 50 mi) from east to west. American reinforcements were able to hold this small area, however, and on Sept. 15, 1950, Gen. MacArthur launched a brilliant amphibious invasion behind enemy lines, striking at the port city of Inch’p[dcl011]n on South Korea’s west coast, about 40 km (about 25 mi) west of Seoul. In a coordinated move, UN forces broke out of the Pusan perimeter. Very quickly the North Koreans were routed and forced above the 38th parallel.

Sensing an opportunity not only to stop but also to roll back Communist expansion, President Truman approved orders for UN forces to cross the 38th parallel and push the enemy above the Yalu River, which separated North Korea from China. Despite repeated warnings from the Chinese that they would enter the war if the Americans came near the Yalu, UN forces crossed into North Korea on October 7 and later captured P’yp[dcl011]ngyang, its capital city. By October 25 some advance units had reached the Yalu; there they came into contact with Chinese “volunteers” who had moved into North Korea. After hard fighting in which MacArthur’s units had to fall back, the Chinese retired and MacArthur continued his offensive.

Shortly thereafter, the Chinese struck again, this time in massive numbers. UN troops, overextended, outnumbered, and ill-equipped to fight a fresh enemy in the bitter Korean winter, were soon in general retreat. On November 26 the Communists cut the escape route of some 40,000 U.S. soldiers and marines in northeast Korea, who fought their way out and were later evacuated from the port of Hŭngnam. The Communists reoccupied P’yp[dcl011]ngyang on December 5 and, sweeping into South Korea, recaptured Seoul on Jan. 4, 1951. Because they had overextended their supply lines and had vastly inferior firepower, they were not able to press their advantage. The Communist offensive was halted by January 15 along a front far south of Seoul.

Even as the Chinese were advancing southward, Truman again redefined American policy in Korea. Unwilling to engage in an all-out war with China, which could have led to a world war involving the Soviet Union and certainly would have alienated the European allies of the U.S., the president abandoned as his objective the military reunification of Korea. He returned to his original goal of stopping Communist aggression in Korea.

The U.S. Eighth Army took the offensive on January 25, and the entire UN command mounted the powerful attack known as Operation Killer on February 21. Under pressure of superior firepower, the Chinese slowly withdrew from South Korea. Seoul fell to the UN again on March 14. By April 22 UN forces had occupied positions slightly north of the 38th parallel along a line that, with minor variations, remained stationary for the rest of the war. Meanwhile, on April 11, Gen. MacArthur, who had publicly advocated a very aggressive military strategy that differed from the president’s policies, had been relieved of his command by Truman. Under his successor, Lt. Gen. Matthew Ridgway (1895–1993), for the next two years the UN forces engaged mainly in a series of probing actions known as the active defense.

Periods of heavy fighting continued, however, both on the ground and in the air. U.S. troop strength remained at around 260,000. Forces from other UN nations stayed at about 35,000, while Republic of Korea (ROK) forces grew from some 280,000 to about 340,000. The Communist forces increased from approximately 500,000 to 865,000, and their armored strength grew from almost nothing to one North Korean and two Chinese armored divisions and one mechanized division, with an estimated 520 tanks. Although the Communists could not sustain another major offensive, their well-entrenched forces made even the UN’s active defense strategy very costly. Some of the most desperate battles took place on the hills called Old Baldy, Capital, Pork Chop, T-Bone, and Heartbreak Ridge.

Air power played a key role in the war, which proved to be the first battlefield in history for supersonic jet aircraft. The Chinese had developed into a major air power. Half of their 1400 aircraft were Soviet-built MiG-15s, generally regarded by military experts as the finest jet aircraft in the world. Operating from bases in Manchuria and seldom venturing over UN lines, the MiG-15s, nevertheless, threatened UN air supremacy over so-called MiG Alley in northwest Korea. Not until the U.S. responded with a crash program that produced the formidable F-86 Sabres did UN forces have aircraft capable of challenging the MiG-15s on approximately equal terms. Large-scale air battles resulted ultimately in the loss of some 58 Sabres and 800 MiGs.

UN aircraft were also instrumental in support of ground forces, in destroying Chinese supply lines, and in crippling North Korean airfields. The UN air force, retaining command of the skies despite opposition from enemy interceptors, devastated North Korean supply bases, railroads, bridges, hydroelectric plants, and industrial centers. North Korean coastal points were systematically pounded by UN naval units. The war was marked also by violent riots and demonstrations in the UN prisoner-of-war compounds; by Communist charges, never substantiated, that the U.S. had waged germ warfare against North Korea and China; by the exchange of sick and wounded prisoners of war; and by disclosures that the Communists had been guilty of atrocities against captured UN personnel.

In June 1951, as the positional-warfare pattern began to crystallize, the Soviet delegate to the UN formally proposed that the belligerents in Korea open discussions for a cease-fire. On July 10, 1951, following preparatory talks, representatives of the UN and Communist commands began truce negotiations at Kaesp[dcl011]ng, North Korea. Talks continued intermittently for two years.

Although conducted in an atmosphere of mutual suspicion, negotiations finally resulted in settlement of all but one major issue: Communist refusal to accept the principle, adhered to by the UN, that a prisoner of war should not be returned against his will to his respective army. Negotiations broke down in October 1952 and were not resumed until April 1953. In late spring, the two sides agreed that prisoners unwilling to return to their own countries would be placed in the custody of a neutral commission for a period of 90 days following the signing of a truce. During this period, each nation could attempt to persuade its nationals to return home. The two sides agreed to hold a top-level peace conference within three months of the effective date of the armistice, but this was later postponed until April 1954.

In July 1953, the truce agreement was signed at P’anmunjp[dcl011]m. Thus, pending ultimate settlement at the projected peace conference, the Korean War was terminated after more than three years of conflict. The U.S. suffered some 140,000 casualties; deaths from all causes totaled 36,516, of which 33,686 occurred in combat. South Korea sustained 1,312,836 military casualties, including 415,004 dead; casualties among other UN allies totaled 16,532, including 3094 dead. Estimated Communist casualties were 2 million. The economic and social damage to the Korean nation was incalculable.        B.I.K., BURTON I. KAUFMAN

For further information on this topic, see the Bibliography, section 1079. The Korean War.